def main():
    def n31(a):  # a = initial number
        c = 0
        l = [a]
        while a != 1:
            if a % 2 == 0:  # if even divide it by 2
                a = a // 2
            elif a % 2 == 1:  # if odd 3n+1
                a = 3 * a + 1
            c += 1  # counter
            l += [a]

        return l, c

    print(n31(43))
    print(n31(98)[0][-1])  # = a
    print("It took {0} steps.".format(n31(13)[1]))  # optional finish


if __name__ == '__main__':
    main()
